Add back experimental attribute objc_suppress_protocol_methods (slightly renamed).

This is still an experimental attribute, but I wanted it in tree
for review.  It may still get yanked.

This attribute can only be applied to a class @interface, not
a class extension or category.  It does not change the type
system rules for Objective-C, but rather the implementation checking
for Objective-C classes that explicitly conform to a protocol.
During protocol conformance checking, clang recursively searches
up the class hierarchy for the set of methods that compose
a protocol.  This attribute will cause the compiler to not consider
the methods contributed by a super class, its categories, and those
from its ancestor classes.  Thus this attribute is used to force
subclasses to redeclare (and hopefully re-implement) methods if
they decide to explicitly conform to a protocol where some of those
methods may be provided by a super class.

This attribute intentionally leaves out properties, which are associated
with state.  This attribute only considers methods (at least right now)
that are non-property accessors.  These represent methods that "do something"
as dictated by the protocol.  This may be further refined, and this
should be considered a WIP until documentation gets written or this
gets removed.

llvm-svn: 195533

2 files changed, 32 insertions, 3 deletions

diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 1dec334bc7e..7ae873d7f9e 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -2134,6 +2134,28 @@ static void handleObjCRootClassAttr(Sema &S, Decl *D,
                                Attr.getAttributeSpellingListIndex()));
 }
 
+static void handleObjCSuppresProtocolAttr(Sema &S, Decl *D,
+                                          const AttributeList &Attr) {
+  if (!isa<ObjCInterfaceDecl>(D)) {
+    S.Diag(Attr.getLoc(), diag::err_attribute_wrong_decl_type)
+      << Attr.getName() << ExpectedObjectiveCInterface;
+    return;
+  }
+
+  IdentifierLoc *Parm = (Attr.getNumArgs() == 1 && Attr.isArgIdent(0))
+                        ? Attr.getArgAsIdent(0) : 0;
+
+  if (!Parm) {
+    S.Diag(D->getLocStart(), diag::err_objc_attr_not_id) << Attr.getName() << 1;
+    return;
+  }
+
+  D->addAttr(::new (S.Context)
+             ObjCSuppressProtocolAttr(Attr.getRange(), S.Context, Parm->Ident,
+                                      Attr.getAttributeSpellingListIndex()));
+}
+
+
 static void handleObjCRequiresPropertyDefsAttr(Sema &S, Decl *D,
                                                const AttributeList &Attr) {
   if (!isa<ObjCInterfaceDecl>(D)) {
@@ -4713,7 +4735,10 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case AttributeList::AT_ObjCRootClass:
     handleObjCRootClassAttr(S, D, Attr);
     break;
-  case AttributeList::AT_ObjCRequiresPropertyDefs: 
+  case AttributeList::AT_ObjCSuppressProtocol:
+    handleObjCSuppresProtocolAttr(S, D, Attr);
+    break;
+  case AttributeList::AT_ObjCRequiresPropertyDefs:
     handleObjCRequiresPropertyDefsAttr (S, D, Attr); 
     break;
   case AttributeList::AT_Unused:      handleUnusedAttr      (S, D, Attr); break;
diff --git a/clang/lib/Sema/SemaDeclObjC.cpp b/clang/lib/Sema/SemaDeclObjC.cpp
index 95e3b4f4669..6de4e5bb21a 100644
--- a/clang/lib/Sema/SemaDeclObjC.cpp
+++ b/clang/lib/Sema/SemaDeclObjC.cpp
@@ -1667,7 +1667,9 @@ void Sema::CheckProtocolMethodDefs(SourceLocation ImpLoc,
           (!Super || !Super->lookupMethod(method->getSelector(),
                                           true /* instance */,
                                           false /* shallowCategory */,
-                                          true /* followsSuper */))) {
+                                          true /* followsSuper */,
+                                          NULL /* category */,
+                                          PDecl /* protocol */))) {
             // If a method is not implemented in the category implementation but
             // has been declared in its primary class, superclass,
             // or in one of their protocols, no need to issue the warning. 
@@ -1703,7 +1705,9 @@ void Sema::CheckProtocolMethodDefs(SourceLocation ImpLoc,
         (!Super || !Super->lookupMethod(method->getSelector(),
                                         false /* class method */,
                                         false /* shallowCategoryLookup */,
-                                        true  /* followSuper */))) {
+                                        true  /* followSuper */,
+                                        NULL /* category */,
+                                        PDecl /* protocol */))) {
       // See above comment for instance method lookups.
       if (C && IDecl->lookupMethod(method->getSelector(),
                                    false /* class */,